HSBC said it was a change in policy, implemented in November, which would now be reviewed.

Stephen Cotton told MoneyBox that he wanted to withdraw £7,000 from HSBC to pay a loan back from his mother.

"When we presented them with the withdrawal slip, they declined to give us the money because we could not provide them with a satisfactory explanation for what the money was for. They wanted a letter from the person involved," he said.

"So I wrote out a few slips. I said, 'Can I have £5,000?' They said no. I said, 'Can I have £4,000?' They said no. And then I wrote one out for £3,000 and they said, 'OK, we'll give you that.'

"I've been banking in that bank for 28 years. They all know me in there. You shouldn't have to explain to your bank why you want that money. It's not theirs, it's yours."

The BBC said numerous others had reported problems, including a man being asked to provided booking receipts for his holiday, and quotes from builders, before they could get cash.

"In short, they refuse to give me my cash. HSBC say it is new internal rules to help prevent money laundering. But for example, what if I want to buy a £5,000 car? It said I’d have to put down a deposit and show them the receipt first."

The new policy has had a furious reaction on social media:

Any bank that asks me the reason I want my own money can piss right off. Won't be opening my business a/c with HSBC, then.

HSBC said in a statement: "We ask our customers about the purpose of large cash withdrawals when they are unusual and out of keeping with the normal running of their account.

"Since last November, in some instances we may have also asked these customers to show us evidence of what the cash is required for."

"The reason being we have an obligation to protect our customers, and to minimise the opportunity for financial crime. However, following feedback, we are immediately updating guidance to our customer facing staff to reiterate that it is not mandatory for customers to provide documentary evidence for large cash withdrawals, and on its own, failure to show evidence is not a reason to refuse a withdrawal.

"We are writing to apologise to any customer who has been given incorrect information and inconvenienced."